A1 Definitions Flashcards
Acid
A species that releases H+ ions in aqueous solution
Activation energy Ea
The minimum energy required to start a reaction by the breaking of bonds
Actual yield
The amount of product obtained from a reaction
Addition polymerisation
Formation of a very long molecular chain (addition polymer) by repeated addition reactions of many unsaturated alkene molecules called monomers
Addition reaction
A reaction in which a reactant is added to an unsaturated molecule to make one saturated molecule
Adsorption
The process that occurs when a gas or liquid or solute is held onto the surface of a solid
Alicyclic
Containing carbon atoms joined together in a ring that is not aromatic
Aliphatic
Containing carbon atoms joined together in unbranched (straight) or branched chains
Alkali
A type of base that dissolves in water to release hydroxide ions
Alkanes
The hydrocarbon homologous series with the general formula CnH2n+2
Alkenes
The hydrocarbon homologous series with one double carbon to carbon bond and the general formula CnH2n
Alkyl group
A side chain formed by removing a hydrogen atom from an alkane parent chain. Any alkyl group is often shown as ‘R’
Alkynes
The hydrocarbon homologous series with one triple carbon-to-carbon bond and the general formula CnH2n-2
Amount of substance n
The quantity whose unit of the mole. Chemists use amount of substance as a means of counting atoms.
Anhydrous
Containing no water molecules
Anion
A negatively charged ion with more electrons than protons
Aromatic
Containing one or more benzene rings
Atom economy
Sum of molar mass of desired products/ Sum of molar mass of all products, MULTIPY BY 100 FOR A PERCENTAGE
Atomic number Z
The number of protons in the nucleus of an atom
Atomic orbital
A region around the nucleus that can hold up to two electrons, with opposite spins
Average bond enthalpy
The average enthalpy change that takes place when breaking by homolytic fission one mole of a given type of bond in the molecules of a gaseous species
Avogadro constant NA
6.02x10^23 mol-1, the number of atoms per mole of carbon-12
Avogadro’s hypothesis
Equal volumes of gases at the same temperature and pressure contain the same number of molecules
Base
A compound that neutralises an acid to form a salt
Binary compound
A compound containing two elements only
Bond angle
The angle between two bonds in an atom
Bonded pair
A pair of electrons shared between two atoms to make a covalent bond
Carbocation
An ion that contains a positively charged carbon atom
Catalyst
A substance that increases the rate of a chemical reaction without being used up in the process. A catalyst provides an alternative route for the reaction with a lower activation energy
Cation
A positively charged ion with fewer electrons than protons
Chain reaction
A reaction in which the propagation steps release new radicals that continue the reaction
Cis-trans isomerism
A special type of E/Z isomerism in which there are two non-hydrogen groups and two hydrogen atoms around the C=C double bond
Cis - Z isomer (same side)
Trans - E isomer (different side)
Closed system
A system isolated from its surroundings
Collision theory
Two reacting particles must collide for a reaction to occur and must be in the correct orientation and have sufficient energy to overcome the activation energy of the reaction.
Coordinate bond
A shared pair of electrons in which the bonded pair has been provided by one of the bonding atoms only. Also called a dative covalent bond
Covalent bonding
The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms.
Dative covalent bond
A shared pair of electrons in which the bonded pair has been provided by one of the bonding atoms only. Also called a coordinate bond
Dehydration
An elimination reaction in which water is removed from a saturated molecule to make an unsaturated molecule.
Delocalised electrons
Electrons that are shared between more than two atoms
Desorption
Release of an adsorbed substance from a surface
Dipole
A separation in electrical charge so that one atom of a polar covalent bond, or one end of a polar molecule, has a small positive charge 𝛿+ and the other has a small negative charge 𝛿-
Dipole-dipole force
An attractive force between permanent dipoles in neighbouring polar molecules.
Displacement reaction
A reaction in which a more reactive element displaces a less reactive element from an aqueous solution of its ions
Displayed formula
A formula that shows the relative positioning of all the atoms in a molecule and the bonds between them.
Disproportionation
A redox reaction in which the same element is both oxidised and reduced
Dynamic equilibrium
The equilibrium that exists in a closed system when the rate of the forward reaction is equal to the rate of the reverse reaction and concentrations do not change
E/Z isomerism
A type of stereoisomerism in which different groups attached to each carbon of a C=C double bond may be arranged differently in space because of the restricted rotation of the C=C bond
Electron configuration
A shorthand method for showing how electrons occupy sub-shells in an atom.
Electronegativity
A measure of the attraction of a bonded atom for the pair of electrons in a covalent bond
Electrophile
An atom or group of atoms which is attracted to an electron-rich centre where it accepts a pair of electrons
Electrophilic addition
An addition reaction in which the first step is attack by an electrophile on a region of high electron density
Elimination reaction
The removal of a molecule from a saturated molecule to make an unsaturated molecule
Empirical formula
A formula that shows the simplest whole-number ratio of atoms of each element present in a compound
End point
The point in a titration where the indicator changes colour; the end point indicates when the reaction is just complete
Endothermic reaction
A reaction in which the enthalpy of the products is greater than the enthalpy of the reactants resulting in heat being taken in from the surroundings (ΔH is positive)
Enthalpy
The heat content that is stored in a chemical system
Enthalpy change ΔH
Difference in enthalpy between reactants and products in a reaction
Enthalpy cycle
A diagram showing alternative routes between reactants and products which allows the indirect determination of an enthalpy change from other known enthalpy changes using Hess’ law.
Enthalpy profile diagram
A diagram for a reaction to compare the enthalpy of the reactants with the enthalpy of the products
Equilibrium constant Kc
A measure of the position of equilibrium; the magnitude of an equilibrium constant indicates whether there are more reactants or more products in an equilibrium system
Exothermic reaction
A reaction in which the enthalpy of the products is smaller than the enthalpy of the reactants resulting in heat loss to the surroundings ΔH is negative
Fingerprint region
An area of an infrared spectrum below 1500cm^-1 that gives a characteristic pattern for different compounds
First ionisation energy
The energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions
Fractional distillation
The separation of components in a liquid mixture by their different boiling points into fractions with different compositions
Fragment ions
Ions formed from the breakdown of the molecular ion in a mass spectrometer
Fragmentation
The process in mass spectrometry that causes a positive ion to split into smaller pieces, one of which is a positive fragment ion.
Functional group
The part of the organic molecule responsible for its chemical reactions
General formula
The simplest algebraic formula of a member of a homologous series.
Giant covalent lattice
A three-dimensional structure of atoms, bonded together by strong covalent bonds
Giant ionic lattice
A three-dimensional structure of atoms, bonded together by strong covalent bonds
Giant ionic lattice
A three dimensional structure of atoms, bonded together by strong ionic bonds
Giant metallic lattice
A three-dimensional structure of positive ions and delocalised electronsm bonded together by strong metallic bonds
Group
A vertical column in the periodic table.
Elements in a group have similar chemical properties and their atoms have the same number of outer shell electrons
Hess’ law
If a reaction can take place by more than one route and the initial and final conditions are thee same, the total enthalpy change is the same for each route
Heterogeneous catalysis
A reaction in which the catalyst has a different physical state from the reactants; frequently reactants are gases whilst the catalyst is a solid
Heterolytic fission
The breaking of a covalent bond forming a cation (+) and an anion (-)
Homogeneous catalysis
A reaction in which the catalyst and reactants are in the same physical state, which is most frequently the aqueous or gaseous state
Homologous series
A series of organic compounds with the same functional group but with each successive member differing by CH2
Homolytic fission
The breaking of a covalent bond with one of the bonded electrons going to each atom, forming two radicals
Hydrated
A crystalline compound containing water molecules
Hydrocarbon
A compound containing carbon and hydrogen only
Hydrogen bond
A strong dipole dipole attraction between an electron-deficient hydrogen atom of -NH, -OH, or HF on one molecule and a lone pair of electrons on a highly electronegative atom containing N, O or F on a different molecule
Hydrolysis
A reaction with water that breaks a chemical compound into two compounds, the H and OH in a water molecule becomes incorporated into the two compounds
Induced dipole-dipole interaction
Attractive forces between induced dipoles in different molecules, also known as LONDON FORCES
Initiation
The first stage in a radical reaction in which radicals start when a covalent bond is broken by homolytic fission of a covalent bond
Intermediate
A species formed during a reaction that reacts further and is not present in the final products
Intermolecular forces
An attractive force between molecules. Intermolecular forces can be London Forces, Permanent Dipole-Dipole Interactions or Hydrogen Bonding
Ion
A positively or negatively charged atom or a covalently bonded group of atoms (polyatomic ion), where the number of electrons is different from the number of protons.
Ionic bonding
The electrostatic attraction between oppositely charged ions.
Isotope
Atoms of the same element with different numbers of neutrons and different masses.
Le Chatelier’s principle
When a system in dynamic equilibrium is subjected to an external change, the system readjusts itself to minimise the effect of the change and to restore equilibrium
Limiting reagent
The reactant that is not in excess, which will be used up first and stop the reaction
London forces
Attractive forces between induced dipoles in different molecules; also known as induced dipole-dipole interactions
Lone pair
An outer shell pair of electrons that is not involved in chemical bonding
Mass number A
The sum of the number of protons and neutrons in trhe nucleus; also known as a nucleon number
Metallic bonding
The electrostatic attraction between positive metal ions and delocalised electrons
Concentration
The amount of solute, in moles, dissolved in 1dm^3 of solution
Molar gas volume Vm
The volume per mole of gas molecules at a stated temperature and pressure.
Molar mass M
The mass per mole of a substance in units of g mol^-1
Mole
The amount of any substance containing as many elementary particles as there are carbon atoms in exactly 12g of the carbon-12 isotope, ie. 8.02x^23 particles
Molecular formula
A formula that shows the number and type of atoms of each element present in a molecule
Molecular ion
The positive ion formed in mass spectrometry when a molecule loses an electron
Molecule
The smallest part of a covalent compound that can exist while retaining its chemical identity, consisting of two or more atoms covalently bonded together
Monomer
A small molecule that combines with many other monomers to form a polymer
Neutralisation
The reaction between an acid and a base to produce a salt
Nomenclature
A system of naming compounds
Non-polar
With no charge separation across a bond or in a molecule
Nucleon number
The number of protons and neutrons in an atom
Nucleophile
An atom or group of atoms that is attracted to an electron-deficient carbon atom where it donates a pair of electrons to form a new covalent bond
Nucleophilic substitution
A reaction in which a nucleophile is attracted to an electron-deficient carbon atom and replaces an atom or group of atoms on it
Oxidation
Loss of electrons or an increase in oxidation number
Oxidation number
A measure of the number of electrons that n atom uses to bond with atoms of another element. Oxidation numbers are derived from a set of rules
Oxidation state
The oxidation number
Oxidising agent
A reagent that oxidises (takes electrons from) another species
π-bond
A bond formed by the sideways overlap of two p orbitals, containing two electrons and with the electron density concentrated above and below the line joining the nuclei of the bonding atoms
Partial dissociation
The splitting of some of a species in solution into aqueous ions
Pauling electronegativity value
A value assigned as a measure of the relative attraction of a bonded atom for the pair of electrons in a covalent bond
Percentage yield
Actual yield divided by theoretical yield
Multiply by 100
Periodicity
A repeating trend in properties of the elements across each period of the periodic table
Periods
A horizontal row of elements in the periodic table. Elements show trend in properties across a period
Permanent dipole
A small charge difference that does not change across a bond, with positive and negative partial changes on the bonded atoms: the result of the bonded atoms having different electronegativities
Permanent dipole-dipole interactions
Attractive forces between the permanent dipoles in different molecules
Polar molecule
A molecule with an overall dipole, having taken into account any dipoles across bonds and the shape of the molecule
Polar covalent bond
A bond with a permanent dipole, having positive and negative partial charges on the bonded atoms
Polyatomic ion
An ion containing more than only one atom.
Polymer
A large molecule formed from many thousands of repeat units of smaller molecules known as monomers
Position of equilibrium
The relative quantities of reactants and products, indicating the extent of a reversible reaction at equilibrium
Primary
On a carbon atom at the end of a chain
Primary alcohol
An alcohol in which the -OH group is attached to a carbon atom that is attached to two or three hydrogen atoms
Principle quantum number n
A number representing the relative overall energy of each orbital, which increases with distance from the nucleus. The sets of orbitals with the same n-value are referred to as electron shells or energy levels
Propagation
the steps that continue a free radical reaction in which a radical reacts with a reactant molecule to form a new molecule and another radical, causing a chain reaction
Proton number
The number of protons in the nucleus of an atom; also known as atomic number
Radical
A species with an unpaired electron
Rate of reaction
The change in concentration of a reactant or a product in a given time
Reaction mechanism
The sequence of bond breaking and bond-forming steps that shows the path taken by electrons during a reaction
Redox reaction
A reaction involving reduction and oxidation
Reducing agent
A reagent that reduces (adds electron to) another species
Reduction
Gain of electrons or a decrease in oxidation number
Reflux
The continual boiling and condensing of a reaction mixture back to the original container to ensure that the reaction takes place without the contents of the flask boiling dry
Relative atomic mass Ar
The weighted mean mass of an atom of an element compared with one-twelfth of the mass of an atom of carbon-12
Relative formula mass
The weighted mean mass of the formula unit of a compound compared with one-twelfth of the mass of an atom of carbon-12
Relative isotopic mass
The mass of an isotope compared with one-twelfth of the mass of an atom of carbon-12
Relative molecular mass Mr
The weighted mean mass of a molecule of a compound compared with one-twelfth of the mass of an atom of carbon-12
Reversible reaction
A reaction that takes place in both forward and reverse directions
σ-bond
Sigma bond, a bond formed by the overlap of one orbital from each bonding atom, consisting of two electrons and with the electron density centred around a line directly between the nuclei of the two atoms
Salt
The product of a reaction in which the H+ ions from the acid are replaced by metal or ammonium ions
Saturated
Containing single bonds only
Saturated hydrocarbon
A hydrocarbon with single bonds only
Second ionisation energy
The energy required to remove one electron from each ion in one mole of gaseous 1+ ions of an element to form one mole of gaseous 2+ ions
Secondary
On a carbon atom to which two carbon chains are attached
Shell (electron shell)
A group of atomic orbitals with the same principal quantum number n. Also known as a main energy level
Shielding effect
The repulsion between electrons in different inner shells. Shielding reduces the net attractive force between the positive nucleus on the outer shell electrons
Simple molecular lattice
A three-dimensional structure of molecules, bonded together by weak intermolecular forces
Skeletal formula
A simplified organic formula, with hydrogen atoms removed from alkyl chains, leaving just a carbon skeleton and associated functional groups
Specific heat capacity, c
The energy required to raise the temperature of 1g of a substance by 1K
Standard enthalpy change of combustion ΔcH°
The enthalpy change that occurs when one mole of a substance reacts completely with oxygen under standard conditions, with all reactants and products in their standard states
Standard enthalpy change of formation ΔfH°
The enthalpy change that occurs when one mole of a compound is formed from its elements under standard conditions, with all reactants and products in their standard states
Standard enthalpy change of neutralisation ΔneutH°
The enthalpy change that accompanies the reaction of an acid by a base to form one mole of H2O(l), under standard conditions, with all reactants and products in their standard states.
Standard enthalpy change of reaction ΔrH°
The enthalpy change that accompanies a reaction in the molar quantities shown in a chemical equation under standard conditions, with all reactants and products in their standard states
Standard solution
A solution of known concentration
Standard state
The physical state of a substance under standard conditions of 100kPa and a stated temperature (usually 298K)
Stereoisomers
Compounds with the same structural formula but with a different arrangement of the atoms in space
Stoichiometry
The ratio of the amount, in moles, of each substance in a chemical reaction
Strong acid
An acid that dissociates completely in solution
Structural formula
A formula showing the minimal detail for the arrangement of atoms in a molecule
Structural isomers
Compounds with the same molecular formula but different structural formulae
Sub-shell
A group of orbitals of the same type within a shell
Substitution reaction
A reaction in which one atom or group of atoms ins replaced by another atom or group of atoms
Surroundings
Everything that is not the chemical system
System
Everything - the atoms, molecules, or ions - making up the chemical compounds being studied
Termination
The step at the end of a radical substitution when two radicals combine to form a molecule
Tertiary
On a carbon atom to which three carbon chains are attached
Tertiary alcohol
An alcohol in which the -OH group is attached to a carbon atom that is attached to no hydrogen atoms
Theoretical yield
The yield resulting from complete conversion of reactants into products
Unsaturated
Containing a multiple carbon-to-carbon bond
Water of crystallisation
Water molecules that are bonded into a crystalline structure of a compound
Weak acid
An acid that dissocates only partially in solution
